This invention relates to the field of video signal processing. More specifically, this invention relates to video signal processing to improve the subjective resolution of video-type information signals when displayed on a video screen.
In many information systems employing video-type displays, the video portion of the system is deliberately designed to provide relatively low maximum resolution of the displayed images, for reasons of economy, speed, or both. For example, in some information processing systems using CRT display terminals and in some video games designed for use with a CRT in which alpha-numeric characters and relatively large images (such as play field boundaries, partitions and the like) are displayed, only relatively low resolution requirements exist for typical images. As a consequence, the video signal processing circuitry need only provide for relatively low resolution and the system is designed accordingly. A typical example for video processing circuitry implemented in digital form employs three bit digital characters to create the serial lines of video information, and such an implementation provides eight levels of grey scale information.
In some low resolution applications, however, it is desirable to maximize the resolution of some images having more detail than the usual display characters. In the past, improved resolution has been provided by modifying each line of video by averaging the amplitude level of adjacent picture elements (pixels). This technique is primarily employed to reduce or eliminate the effect known as "cogging" which occurs when adjacent picture elements vary widely in luminance levels, the observable effect of which is a sharp or abrupt change throughout the video field, producing a sharp-edged jagged image. While the pixel averaging technique has been found to be somewhat effective, this approach is rather complex to implement successfully and produces an image subjectively possessing a "soft" appearance.